Open-loop step motor control system

Abstract

A motor control system that reduces noise while reducing power requirements but providing sufficient torque. A one-phase-on drive mode modified to microstep between "one phase on" positions is used to accelerate the motor in a non-linear manner to a maximum speed. The microstep drive modes have a constant period, and the step rate of the motor is increased by decreasing the number of microsteps in succeeding steps of the motor. A modified full step waveform maintains the motor at the maximum speed, where the current to one winding of the step motor changes polarity within one motor step while the other remains approximately constant providing increased smoothness in the drive and reduced noise. The polarity changes in accordance with the inductance and the compliance voltage of the motor. A one-phase-on waveform modified to include microsteps between "one phase on" positions later decelerates the motor in a non-linear manner, and the motor stops in a detent position until another waveform of steps is delivered to the motor.

What is claimed is:  
     
       1. A control system for controlling the movement of a motor, the system comprising: 
       an energy source; and  
       a controller that applies energy from the energy source to the motor, wherein the controller applies energy to the motor in a “one phase on” drive mode modified to microstep between the “one phase on” positions during movement of the motor, wherein the controller controls the motor by varying the number of microsteps per motor step while maintaining a constant microstep period, and wherein the controller is adapted to apply energy from the energy source to the motor in a non-linear manner during acceleration of the motor.  
     
     
       2. The control system of  claim 1  wherein the controller is adapted to apply energy from the energy source to the motor in an exponential manner during acceleration of the motor. 
     
     
       3. A control system for controlling the movement of a motor, the system comprising: 
       an energy source; and  
       a controller that applies energy from the energy source in a non-linear manner to accelerate the motor through first and second motor steps, wherein the first motor step includes a first plurality of microsteps, and the second motor step includes a second plurality of microsteps, and wherein the first plurality of microsteps is greater than the second plurality of microsteps and the controller maintains a constant microstep period, wherein the controller is adapted to apply energy to the motor from the energy source after acceleration of the motor to a desired speed has been reached with a third number of microsteps per motor step, the controller maintaining a constant microstep period for each of the third number of microsteps, wherein the controller is adapted apply energy to the motor from the energy source during deceleration of the motor from the desired speed with a fourth number of microsteps per motor step, the fourth number of microsteps per motor step exceeding the third number, the controller maintaining a constant microstep period for each of the fourth number of microsteps, and wherein the controller is adapted to apply energy from the energy source to the motor in an exponential manner during acceleration of the motor.  
     
     
       4. In an intravenous delivery system comprising a fluid supply, a fluid supply line, and a fluid pump having a fluid pump step motor providing mechanical movement for operating on the fluid supply line to move fluid through the line, a method for delivering fluid to a patient, comprising the steps of: 
       accelerating the fluid pump step motor in a series of motor steps, wherein a first of said motor steps is divided into a first number of microsteps, and a second of said motor steps is divided into a second number of microsteps, wherein the first number of microsteps is greater than the second number of microsteps, and  
       maintaining a constant microstep period; and  
       applying energy to the motor in an exponential manner during acceleration of the motor.